The present invention relates to an upending system for an elongated tubular element like an offshore foundation pile or a turbine mast.
GB2226539 A discloses a system for offshore construction work wherein a pile is upended using two cranes one of which cranes is connected via a sling to one end of the pile and the other of which cranes is connected via a sling to two spaced apart connection points on the pile but whose line of action is to the other side of the centre of gravity (c) than the sling. A spreader bar maintains the separation between the connection points during upending. The sling is trained around a sheave so that both slings share the load of the pile equally during upending which is achieved by raising or lowering one sling relative to the other. The three point lift arrangement avoids excessive bending stress on the pile.
It is known to upend a pile offshore wherein an outboard end of a pile rests on a support where around the pile cants. During upending an outboard end is supported by a cable provided with a hook.
GB2394498 shows a pivoting frame for installing a wind turbine on a structure directly onto a submerged pile using an A-frame that can be moved using a winch-cable system. This frame is installed on a vessel on a predetermined fixed position which provides no flexibility during offshore operations.
Mono-piles, like for supporting a wind turbine, have a large diameter like up to 4 to 6 meters and may weigh hundreds of tonnes. These piles are transported from their production site, to for instance a wind turbine park, in a horizontal stance. These piles are finally used in a vertical stance. Therefore, these piles are upended from a horizontal to a vertical stance on site. This upending is a difficult task since such a pile is a thin walled structure and prone to local bending stresses. In addition, outboard operations in the proximity of the pile may be dangerous for personnel.